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PCI(4) FreeBSD Kernel Interfaces Manual PCI(4)
NAMEpci -- generic PCI bus driver
SYNOPSIS
To compile the PCI bus driver into the kernel, place the following line
in your kernel configuration file:
devicepci
To compile in support for Single Root I/O Virtualization (SR-IOV):
optionsPCI_IOV
To compile in support for native PCI-express HotPlug:
optionsPCI_HPDESCRIPTION
The pci driver provides support for PCI devices in the kernel and limited
access to PCI devices for userland.
The pci driver provides a /dev/pci character device that can be used by
userland programs to read and write PCI configuration registers. Pro-
grams can also use this device to get a list of all PCI devices, or all
PCI devices that match various patterns.
Since the pci driver provides a write interface for PCI configuration
registers, system administrators should exercise caution when granting
access to the pci device. If used improperly, this driver can allow
userland applications to crash a machine or cause data loss.
The pci driver implements the PCI bus in the kernel. It enumerates any
devices on the PCI bus and gives PCI client drivers the chance to attach
to them. It assigns resources to children, when the BIOS does not. It
takes care of routing interrupts when necessary. It reprobes the unat-
tached PCI children when PCI client drivers are dynamically loaded at
runtime. The pci driver also includes support for PCI-PCI bridges, vari-
ous platform-specific Host-PCI bridges, and basic support for PCI VGA
adapters.
IOCTLS
The following ioctl(2) calls are supported by the pci driver. They are
defined in the header file <sys/pciio.h>.
PCIOCGETCONF This ioctl(2) takes a pci_conf_io structure. It allows
the user to retrieve information on all PCI devices in
the system, or on PCI devices matching patterns supplied
by the user. The call may set errno to any value speci-
fied in either copyin(9) or copyout(9). The pci_conf_io
structure consists of a number of fields:
pat_buf_len The length, in bytes, of the buffer
filled with user-supplied patterns.
num_patterns The number of user-supplied patterns.
patterns Pointer to a buffer filled with user-sup-
plied patterns. patterns is a pointer to
num_patternspci_match_conf structures.
The pci_match_conf structure consists of
the following elements:
pc_sel PCI domain, bus, slot and
function.
pd_name PCI device driver name.
pd_unit PCI device driver unit number.
pc_vendor PCI vendor ID.
pc_device PCI device ID.
pc_class PCI device class.
flags The flags describe which of
the fields the kernel should
match against. A device must
match all specified fields in
order to be returned. The
match flags are enumerated in
the pci_getconf_flags struc-
ture. Hopefully the flag val-
ues are obvious enough that
they do not need to described
in detail.
match_buf_len Length of the matches buffer allocated by
the user to hold the results of the
PCIOCGETCONF query.
num_matches Number of matches returned by the kernel.
matches Buffer containing matching devices
returned by the kernel. The items in
this buffer are of type pci_conf, which
consists of the following items:
pc_sel PCI domain, bus, slot and
function.
pc_hdr PCI header type.
pc_subvendor PCI subvendor ID.
pc_subdevice PCI subdevice ID.
pc_vendor PCI vendor ID.
pc_device PCI device ID.
pc_class PCI device class.
pc_subclass PCI device subclass.
pc_progif PCI device programming
interface.
pc_revid PCI revision ID.
pd_name Driver name.
pd_unit Driver unit number.
offset The offset is passed in by the user to
tell the kernel where it should start
traversing the device list. The value
passed out by the kernel points to the
record immediately after the last one
returned. The user may pass the value
returned by the kernel in subsequent
calls to the PCIOCGETCONF ioctl. If the
user does not intend to use the offset,
it must be set to zero.
generation PCI configuration generation. This value
only needs to be set if the offset is
set. The kernel will compare the current
generation number of its internal device
list to the generation passed in by the
user to determine whether its device list
has changed since the user last called
the PCIOCGETCONF ioctl. If the device
list has changed, a status of
PCI_GETCONF_LIST_CHANGED will be passed
back.
status The status tells the user the disposition
of his request for a device list. The
possible status values are:
PCI_GETCONF_LAST_DEVICE
This means that there are no more devices
in the PCI device list matching the spec-
ified criteria after the ones returned in
the matches buffer.
PCI_GETCONF_LIST_CHANGED
This status tells the user that the PCI
device list has changed since his last
call to the PCIOCGETCONF ioctl and he
must reset the offset and generation to
zero to start over at the beginning of
the list.
PCI_GETCONF_MORE_DEVS
This tells the user that his buffer was
not large enough to hold all of the
remaining devices in the device list that
match his criteria.
PCI_GETCONF_ERROR
This indicates a general error while ser-
vicing the user's request. If the
pat_buf_len is not equal to num_patterns
times sizeof(structpci_match_conf),
errno will be set to EINVAL.
PCIOCREAD This ioctl(2) reads the PCI configuration registers
specified by the passed-in pci_io structure. The pci_io
structure consists of the following fields:
pi_sel A pcisel structure which specifies the domain,
bus, slot and function the user would like to
query. If the specific bus is not found,
errno will be set to ENODEV and -1 returned
from the ioctl.
pi_reg The PCI configuration register the user would
like to access.
pi_width The width, in bytes, of the data the user
would like to read. This value may be either
1, 2, or 4. 3-byte reads and reads larger
than 4 bytes are not supported. If an invalid
width is passed, errno will be set to EINVAL.
pi_data The data returned by the kernel.
PCIOCWRITE This ioctl(2) allows users to write to the PCI specified
in the passed-in pci_io structure. The pci_io structure
is described above. The limitations on data width
described for reading registers, above, also apply to
writing PCI configuration registers.
PCIOCBARMMAP This ioctl(2) command allows userspace processes to
mmap(2) the memory-mapped PCI BAR into its address
space. The input parameters and results are passed in
the pci_bar_mmap structure, which has the following
fields:
uint64_tpbm_map_base
Reports the established mapping base to the
caller. If PCIIO_BAR_MMAP_FIXED flag was
specified, then this field must be filled
before the call with the desired address for
the mapping.
uint64_tpbm_map_length
Reports the mapped length of the BAR, in
bytes. Its .Vt uint64_t value is always mul-
tiple of machine pages.
int64_tpbm_bar_length
Reports length of the bar as exposed by the
device.
intpbm_bar_off
Reports offset from the mapped base to the
start of the first register in the bar.
structpciselpbm_sel
Should be filled before the call. Describes
the device to operate on.
intpbm_reg
The BAR index to mmap.
intpbm_flags
Flags which augments the operation. See
below.
intpbm_memattr
The caching attribute for the mapping. Typi-
cal values are VM_MEMATTR_UNCACHEABLE for con-
trol registers BARs, and
VM_MEMATTR_WRITE_COMBINING for frame buffers.
Regular memory-like BAR should be mapped with
VM_MEMATTR_DEFAULT attribute.
Currently defined flags are:
PCIIO_BAR_MMAP_FIXED The resulted mappings should be
established at the address
specified by the pbm_map_base
member, otherwise fail.
PCIIO_BAR_MMAP_EXCL Must be used together with If
the specified base contains
already established mappings,
the operation fails instead of
implicitly unmapping them.
PCIIO_BAR_MMAP_RW The requested mapping allows
both reading and writing.
Without the flag, read-only
mapping is established. Note
that it is common for the
device registers to have side-
effects even on reads.
PCIIO_BAR_MMAP_ACTIVATE (Unimplemented) If the BAR is
not activated, activate it in
the course of mapping. Cur-
rently attempt to mmap an inac-
tive BAR results in error.
LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel, or
stored in loader.conf(5). The current value of these tunables can be
examined at runtime via sysctl(8) nodes of the same name. Unless other-
wise specified, each of these tunables is a boolean that can be enabled
by setting the tunable to a non-zero value.
hw.pci.clear_bars (Defaults to 0)
Ignore any firmware-assigned memory and I/O port resources. This
forces the PCI bus driver to allocate resource ranges for memory
and I/O port resources from scratch.
hw.pci.clear_buses (Defaults to 0)
Ignore any firmware-assigned bus number registers in PCI-PCI
bridges. This forces the PCI bus driver and PCI-PCI bridge
driver to allocate bus numbers for secondary buses behind PCI-PCI
bridges.
hw.pci.clear_pcib (Defaults to 0)
Ignore any firmware-assigned memory and I/O port resource windows
in PCI-PCI bridges. This forces the PCI-PCI bridge driver to
allocate memory and I/O port resources for resource windows from
scratch.
By default the PCI-PCI bridge driver will allocate windows that
contain the firmware-assigned resources devices behind the
bridge. In addition, the PCI-PCI bridge driver will suballocate
from existing window regions when possible to satisfy a resource
request. As a result, both hw.pci.clear_bars and
hw.pci.clear_pcib must be enabled to fully ignore firmware-sup-
plied resource assignments.
hw.pci.default_vgapci_unit (Defaults to -1)
By default, the first PCI VGA adapter encountered by the system
is assumed to be the boot display device. This tunable can be
set to choose a specific VGA adapter by specifying the unit num-
ber of the associated vgapciX device.
hw.pci.do_power_nodriver (Defaults to 0)
Place devices into a low power state (D3) when a suitable device
driver is not found. Can be set to one of the following values:
3 Powers down all PCI devices without a device driver.
2 Powers down most devices without a device driver. PCI
devices with the display, memory, and base peripheral
device classes are not powered down.
1 Similar to a setting of 2 except that storage controllers
are also not powered down.
0 All devices are left fully powered.
A PCI device must support power management to be powered down.
Placing a device into a low power state may not reduce power con-
sumption.
hw.pci.do_power_resume (Defaults to 1)
Place PCI devices into the fully powered state when resuming
either the system or an individual device. Setting this to zero
is discouraged as the system will not attempt to power up non-
powered PCI devices after a suspend.
hw.pci.do_power_suspend (Defaults to 1)
Place PCI devices into a low power state when suspending either
the system or individual devices. Normally the D3 state is used
as the low power state, but firmware may override the desired
power state during a system suspend.
hw.pci.enable_ari (Defaults to 1)
Enable support for PCI-express Alternative RID Interpretation.
This is often used in conjunction with SR-IOV.
hw.pci.enable_io_modes (Defaults to 1)
Enable memory or I/O port decoding in a PCI device's command reg-
ister if it has firmware-assigned memory or I/O port resources.
The firmware (BIOS) in some systems does not enable memory or I/O
port decoding for some devices even when it has assigned
resources to the device. This enables decoding for such
resources during bus probe.
hw.pci.enable_msi (Defaults to 1)
Enable support for Message Signalled Interrupts (MSI). MSI
interrupts can be disabled by setting this tunable to 0.
hw.pci.enable_msix (Defaults to 1)
Enable support for extended Message Signalled Interrupts (MSI-X).
MSI-X interrupts can be disabled by setting this tunable to 0.
hw.pci.enable_pcie_hp (Defaults to 1)
Enable support for native PCI-express HotPlug.
hw.pci.honor_msi_blacklist (Defaults to 1)
MSI and MSI-X interrupts are disabled for certain chipsets known
to have broken MSI and MSI-X implementations when this tunable is
set. It can be set to zero to permit use of MSI and MSI-X inter-
rupts if the chipset match is a false positive.
hw.pci.iov_max_config (Defaults to 1MB)
The maximum amount of memory permitted for the configuration
parameters used when creating Virtual Functions via SR-IOV. This
tunable can also be changed at runtime via sysctl(8).
hw.pci.realloc_bars (Defaults to 0)
Attempt to allocate a new resource range during the initial
device scan for any memory or I/O port resources with firmware-
assigned ranges that conflict with another active resource.
hw.pci.usb_early_takeover (Defaults to 1 on amd64 and i386)
Disable legacy device emulation of USB devices during the initial
device scan. Set this tunable to zero to use USB devices via
legacy emulation when using a custom kernel without USB con-
troller drivers.
hw.pci_D_._B_._S_.INT_P_.irq
These tunables can be used to override the interrupt routing for
legacy PCI INTx interrupts. Unlike other tunables in this list,
these do not have corresponding sysctl nodes. The tunable name
includes the address of the PCI device as well as the pin of the
desired INTx IRQ to override:
<D> The domain (or segment) of the PCI device in decimal.
<B> The bus address of the PCI device in decimal.
<S> The slot of the PCI device in decimal.
<P> The interrupt pin of the PCI slot to override. One of
`A', `B', `C', or `D'.
The value of the tunable is the raw IRQ value to use for the INTx
interrupt pin identified by the tunable name. Mapping of IRQ
values to platform interrupt sources is machine dependent.
DEVICE WIRING
You can wire the device unit at a given location with device.hints.
Entries of the form hints._name_._unit_.at="pci_B_:_S_:_F_" or
hints._name_._unit_.at="pci_D_:_B_:_S_:_F_" will force the driver name to
probe and attach at unit unit for any PCI device found to match the spec-
ification, where:
<D> The domain (or segment) of the PCI device in decimal. Defaults
to 0 if unspecified
<B> The bus address of the PCI device in decimal.
<S> The slot of the PCI device in decimal.
<F> The function of the PCI device in decimal.
The code to do the matching requires an exact string match. Do not spec-
ify the angle brackets (< >) in the hints file. Wiring multiple devices
to the same name and unit produces undefined results.
Examples
Given the following lines in /boot/device.hints:
hint.nvme.3.at="pci6:0:0"hint.igb.8.at="pci14:0:0" If there is a device
that supports igb(4) at PCI bus 14 slot 0 function 0, then it will be
assigned igb8 for probe and attach. Likewise, if there is an nvme(4)
card at PCI bus 6 slot 0 function 0, then it will be assigned nvme3 for
probe and attach. If another type of card is in either of these loca-
tions, the name and unit of that card will be the default names and will
be unaffected by these hints. If other igb or nvme cards are located
elsewhere, they will be assigned their unit numbers sequentially, skip-
ping the unit numbers that have 'at' hints.
FILES
/dev/pci Character device for the pci driver.
SEE ALSOpciconf(8)HISTORY
The pci driver (not the kernel's PCI support code) first appeared in
FreeBSD 2.2, and was written by Stefan Esser and Garrett Wollman. Sup-
port for device listing and matching was re-implemented by Kenneth Merry,
and first appeared in FreeBSD 3.0.
AUTHORS
Kenneth Merry <ken@FreeBSD.org>
BUGS
It is not possible for users to specify an accurate offset into the
device list without calling the PCIOCGETCONF at least once, since they
have no way of knowing the current generation number otherwise. This
probably is not a serious problem, though, since users can easily narrow
their search by specifying a pattern or patterns for the kernel to match
against.
FreeBSD Ports 11.2 June 14, 2018 FreeBSD Ports 11.2